This is a pharmacokinetics study for patients who are HIV positive and treated with Antiretroviral therapy. It is designed to look at which combinations of anti-HIV drugs are the safest and most effective way to treat HIV infection over a long period of time. It will evaluate if the initial use of two NRTI (nucleoside analog reverse transcriptase inhibitor) and Nelfinavir followed by two different NRTIs and Efavirenz is superior to the initial use of two NRTI's plus Efavirenz followed by different NRTIs and NFV. The study is being done to learn how well different combinations of drugs can decrease the amount of HIV in the blood.